A method for preparing lightweight and high-strength foamed ceramic material using waste residue and the product obtained

Abstract

The present invention discloses a method for preparing a lightweight, high-strength foamed ceramic material using waste slag, and the product obtained. The raw material composition of the foamed ceramic material is 51.3-69.3wt% of metal slag, 14.8-21.4wt% of feldspar, 1.0-1.7wt% of a foaming agent, and 14.9-25.6wt% of a buffer; the buffer is fly ash beads or fly ash with a bead content greater than 80wt%. The present invention utilizes fly ash beads from power plants as a buffer and controls secondary crystallization through a process, so that the foamed ceramic product has good compressive strength and performance at a relatively low volume density, realizing the resource utilization of solid waste and having both lightweight and high-strength mechanical properties. The preparation process of the present invention is simple, low-cost, quality-controllable, and easy to industrialize and mass-produce.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a method for preparing a lightweight and high-strength foamed ceramic material by utilizing waste residues and a product obtained therefrom. Background Art

[0002] Foamed ceramics are a new type of inorganic material, created through a foaming process, with a glassy phase as the primary crystalline phase. Due to their low bulk density and thermal conductivity, as well as excellent corrosion resistance, aging resistance, and fire resistance, they are widely used in construction, environmental protection, and other fields. Their production method primarily involves adding a foaming agent to a green body formulation and sintering it at high temperatures to generate gases. These gases are then encapsulated by the high-temperature molten liquid phase. Upon cooling, the green body forms closed honeycomb-like pores within the body, resulting in the foamed ceramic product.

[0003] At present, industrially produced foamed ceramics mostly use silicon carbide or mineral raw materials that can produce gas as foaming agents, such as carbonates, sulfates, and multi-source composite foaming agents. The firing temperature is mostly at 1160±30℃. The key to the technology lies in the control of the molten liquid phase in the high-temperature stage. Too high or too low will affect the liquid phase viscosity and thus affect the size and distribution of bubbles, and thus affect the mechanical and thermal insulation properties of the product.

[0004] The bulk density and compressive strength of foamed ceramics are important performance indicators, and the two balance each other. The brittleness (mechanical properties) of foamed ceramics has affected the promotion and application of its products to a certain extent. Foamed ceramics are composed of a solid ceramic matrix and gas phase bubbles. The pore structure and matrix strength determine the mechanical properties of foamed ceramics. In the field of obtaining common bulk density (380+50kg / m 3 ) While developing foamed ceramics, its mechanical and thermal insulation properties can be improved through formula and process control, which is expected to provide a broader space for the promotion of foamed ceramics in application scenarios.

[0005] Existing research mainly focuses on improving the strength of foamed ceramic products by improving the pore structure and pore size distribution uniformity and enhancing the strength of the solid phase matrix (pore wall) of the foamed ceramic. For example, by introducing chromium oxide and / or substances containing chromium oxide as nucleating agents, and supplemented with inorganic chopped fibers as reinforcing agents to improve the strength of foamed ceramics; or, by introducing mullite, cordierite, quartz and α-alumina crystal phases at the raw material end, the physical components of the foamed ceramics are controlled to achieve the purpose of improving the compressive strength of the foamed ceramics. At the same time, other scholars also control the pore structure by means of process means such as layered arrangement of powder particle size. However, these process means are complex and have limited effect on improving the strength of foamed ceramics, and are not easy to implement in practice. At the same time, the existing foamed ceramics still have problems such as a large number of raw materials for preparation, low utilization rate of industrial waste slag, high preparation cost, too much plastic raw material is introduced to make it difficult to form, long firing cycle, waste of fuel and energy, and not conducive to industrial production. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the prior art by providing a method for preparing lightweight, high-strength foamed ceramic materials using waste residues. This method addresses the current problems of low utilization of industrial waste residues, high production costs, and poor material performance in foamed ceramic formulations. Another object of the present invention is to provide products produced using this method.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for preparing a lightweight, high-strength foamed ceramic material using waste slag. The raw materials of the foamed ceramic material are composed of 51.3-69.3 wt% of metal slag, 14.8-21.4 wt% of feldspar, 1.0-1.7 wt% of a foaming agent, and 14.9-25.6 wt% of a buffer. The buffer is fly ash beads or fly ash with a bead content greater than 80 wt%. The preparation method comprises the following steps:

[0009] (1) dry-grinding the metal slag and feldspar to obtain a foamed ceramic base material;

[0010] (2) adding a foaming agent and a buffer to the foamed ceramic base material and stirring and mixing uniformly to obtain a foamed ceramic powder;

[0011] (3) Filling the foamed ceramic powder into a mold, heating it to 1140-1180°C at a rate of 3-8°C / min, and keeping it warm for 60-100 minutes; then cooling it to the crystallization temperature of 950-1000°C at a rate of 2-8°C / min, and keeping it warm for 3-5 hours; and then cooling it to room temperature at a rate of 2-6°C / min to obtain a foamed ceramic material.

[0012] Furthermore, the particle size of the buffer of the present invention is D50=45-55 μm. The particle size of the foamed ceramic base material in step (1) is D50=45-55 μm. The stirring time in step (2) is 30-60 min.

[0013] In the above scheme, the metal slag of the present invention is vanadium-titanium-iron slag and / or molybdenum slag; the feldspar is potassium feldspar and / or sodium feldspar; and the foaming agent is SiC dust collecting powder.

[0014] The product is prepared using the above-mentioned method for preparing lightweight and high-strength foamed ceramic materials using waste residues.

[0015] The present invention has the following beneficial effects:

[0016] (1) The present invention utilizes fly ash containing relatively high levels of Al2O3, SiO2, and CaO, as well as hollow spherical floating beads with a content ranging from 10% to 30%. The high specific surface area of ​​the floating beads allows more gas to combine with the matrix during the foaming process and allows the bubbles to expand around along the shell wall of the floating beads. In the early stage of foaming, the temperature and pressure on the surface of the hollow spheres further expand the pore defects on the shell surface, allowing a portion of the gas to penetrate into the interior of the floating beads, thereby playing a buffering role and reducing the defects caused by continuous gas production during the foaming process. At the same time, during high-temperature melting and foaming, the melt and the floating beads interface fuse, repairing the floating bead surface and further strengthening the floating bead hollow shell structure. Finally, in the cooling stage, through the cooling process control, the nucleating agent such as TiO2 contained in the waste slag raw material induces secondary crystallization, so that the glass phase in the pore wall is further transformed into a crystalline phase, forming a hollow support structure covering the floating beads. While ensuring good pore structure support and pore layout, the mechanical properties of the foamed ceramic are significantly improved.

[0017] (2) The present invention adopts fly ash floating beads and / or fly ash containing floating beads, and while ensuring a good pore structure and layout, promotes the transformation of the glass phase in the matrix into high-strength mullite and quartz crystals through cooling process control, which not only improves the strength of the matrix but also does not affect the formation and growth of pores in the melt at high temperature. The foamed ceramics obtained have a good pore structure and excellent mechanical properties (water absorption rate ≤ 0.35%, volume density > 315kg / m 3 , compressive strength>9.0MPa, thermal conductivity≤0.11W / (m·K)).

[0018] (3) The present invention utilizes fly ash floating beads with a high specific surface area as a foaming buffer, which not only plays the role of low bulk density of the hollow shell structure of the floating beads, but also plays a good bubble buffering role during the firing process. Under the control of cooling process conditions, it promotes crystal growth that is beneficial to improving mechanical strength, and realizes the preparation of lightweight and high-strength foamed ceramics.

[0019] (4) The present invention uses a two-step process of dry grinding of raw materials and mixing of additives, which not only achieves uniform dispersion of powders but also does not damage the structure of fly ash and floating beads. The foamed ceramics obtained have the characteristics of low energy consumption, simple process, and good mechanical properties of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings.

[0021] Figure 1 This is a morphology diagram of the foamed ceramic material prepared in an embodiment of the present invention;

[0022] Figure 2 3 is a SEM image of the foamed ceramic material prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The embodiment of the present invention provides a method for preparing a lightweight, high-strength foamed ceramic material using waste slag. The raw material composition of the foamed ceramic material is 51.3-69.3wt% of metal slag, 14.8-21.4wt% of feldspar, 1.0-1.7wt% of foaming agent, and 14.9-25.6wt% of buffer; the buffer is fly ash beads or fly ash with a bead content of >80wt%.

[0024] The metal slag is vanadium-titanium-iron slag and / or molybdenum slag, the feldspar is potassium feldspar and / or sodium feldspar, and the foaming agent is SiC dust collecting powder.

[0025] The fly ash discharged from the smelting process of coal-fired power plants is dry-sorted and impurities removed by wind classifiers, and the ash with density less than 1.0×10 3 kg / m 3 Hollow fly ash and density ≥1.0×10 3 kg / m 3 Fly ash powder. The fly ash floating beads in the present invention refer to the fly ash powder with a density of less than 1.0×10 3 kg / m 3 The hollow fly ash with a floating bead content of 80wt% refers to a mixture of hollow fly ash and fly ash powder in a mass ratio of 8:2; the fly ash with a floating bead content of 90wt% refers to a mixture of hollow fly ash and fly ash powder in a mass ratio of 9:1; the fly ash with a floating bead content of 40wt% refers to a mixture of hollow fly ash and fly ash powder in a mass ratio of 2:3.

[0026] The chemical compositions of the raw materials used in the examples of the present invention are shown in Table 1.

[0027] Table 1 Chemical composition of raw materials used in the examples of the present invention (wt%)

[0028]

[0029]

[0030] Example 1:

[0031] This embodiment provides a method for preparing a lightweight, high-strength foamed ceramic material using waste slag. The raw materials of the foamed ceramic material are composed of 69.3 wt% of vanadium-titanium iron slag, 14.8 wt% of albite, 1.0 wt% of SiC dust collecting powder (passed through a 325 mesh sieve) as a foaming agent, and 14.9 wt% of a buffering agent. The buffering agent is fly ash beads with a particle size of D50 = 45-55 μm. The preparation method comprises the following steps:

[0032] (1) Dry-grinding the vanadium-titanium iron slag and albite in a ball mill to obtain a foamed ceramic base material with a particle size of D50 = 45 to 55 μm;

[0033] (2) Adding a foaming agent and a buffer to the foamed ceramic base material, mixing, and stirring in a planetary blade mixer for 30 minutes (stirring speed is 140RPM) to obtain a uniform foamed ceramic powder;

[0034] (3) The foamed ceramic powder was filled into a sagger mold covered with refractory fiber paper with a thickness of 8±0.5 mm, and heated to 1160°C at a rate of 5°C / min in a muffle furnace and kept warm for 80 min; then cooled to the crystallization temperature of 980°C at a rate of 6°C / min and kept warm for 4 h; and then cooled to room temperature at a rate of 3°C / min to obtain a foamed ceramic material.

[0035] Example 2:

[0036] This embodiment provides a method for preparing a lightweight, high-strength foamed ceramic material using waste slag. The raw materials of the foamed ceramic material are composed of 59.1 wt% of molybdenum slag, 19.7 wt% of albite, 1.5 wt% of SiC dust collecting powder (passed through a 325 mesh sieve) as a foaming agent, and 19.7 wt% of a buffer. The buffer is fly ash with a particle size D50 of 45 to 55 μm and a 90% floating bead content. The preparation method comprises the following steps:

[0037] (1) Dry-grinding the molybdenum slag and albite in a ball mill to obtain a foamed ceramic base material with a particle size of D50 = 45 to 55 μm;

[0038] (2) Adding a foaming agent and a buffer to the foamed ceramic base material, mixing, and stirring in a planetary blade mixer for 40 minutes (stirring speed is 140RPM) to obtain a uniform foamed ceramic powder;

[0039] (3) The foamed ceramic powder was filled into a sagger mold covered with refractory fiber paper with a thickness of 8±0.5 mm, and heated to 1140°C at a rate of 8°C / min in a muffle furnace and kept warm for 100 min; then cooled to the crystallization temperature of 1000°C at a rate of 8°C / min and kept warm for 3 h; and then cooled to room temperature at a rate of 2°C / min to obtain a foamed ceramic material.

[0040] Example 3:

[0041] This embodiment provides a method for preparing a lightweight, high-strength foamed ceramic material using waste slag. The raw materials of the foamed ceramic material are composed of 51.3 wt% of vanadium-titanium iron slag, 21.4 wt% of potassium feldspar, 1.7 wt% of SiC dust collecting powder (passed through a 325-mesh sieve) as a foaming agent, and 25.6 wt% of a buffer. The buffer is fly ash with a particle size D50 of 45 to 55 μm and a floating bead content of 80%. The preparation method comprises the following steps:

[0042] (1) Dry-grinding the vanadium-titanium iron slag and potassium feldspar in a ball mill to obtain a foamed ceramic base material with a particle size of D50 = 45 to 55 μm;

[0043] (2) Adding a foaming agent and a buffer to the foamed ceramic base material, mixing, and stirring in a planetary blade mixer for 60 minutes (stirring speed is 140RPM) to obtain a uniform foamed ceramic powder;

[0044] (3) The foamed ceramic powder was filled into a sagger mold covered with refractory fiber paper with a thickness of 8±0.5 mm, and heated to 1180°C at a rate of 3°C / min in a muffle furnace and kept warm for 60 min; then cooled to the crystallization temperature of 950°C at a rate of 3°C / min and kept warm for 5 h; and then cooled to room temperature at a rate of 6°C / min to obtain a foamed ceramic material.

[0045] Comparative Example 1:

[0046] Comparative Example 1 differs from Example 1 in that no fly ash beads are added. The raw material composition of the foamed ceramic material of Comparative Example 1 is 81.4 wt% of vanadium-titanium-iron slag, 17.4 wt% of albite, and 1.2 wt% of SiC dust collecting powder (passed through a 325 mesh sieve) as a foaming agent. Other conditions are the same as in Example 1.

[0047] Comparative Example 2:

[0048] The difference between Comparative Example 2 and Example 1 is that the buffer is fly ash (particle size D50 = 45-55 μm) with a floating bead content of 40%. The other conditions are the same as those of Example 1.

[0049] Comparative Example 3:

[0050] Comparative Example 3 differs from Example 1 in that the buffering agent is used in an amount of 10.4 wt %. The raw material composition of the foamed ceramic material in Comparative Example 1 is 72.9 wt % vanadium-titanium-iron slag, 15.7 wt % albite, 1.0 wt % SiC dust collection powder (passed through a 325 mesh sieve) as the foaming agent, and 10.4 wt % buffering agent. The buffering agent is fly ash beads with a particle size D50 of 45-55 μm. All other conditions are the same as in Example 1.

[0051] Comparative Example 4:

[0052] Comparative Example 4 differs from Example 1 in that the buffering agent is used in an amount of 31.7 wt %. The raw material composition of the foamed ceramic material in Comparative Example 1 is 55.6 wt % vanadium-titanium-iron slag, 11.9 wt % albite, 0.8 wt % SiC dust collection powder (passed through a 325 mesh sieve) as the foaming agent, and 31.7 wt % buffering agent. The buffering agent is fly ash beads with a particle size D50 of 45-55 μm. All other conditions are the same as in Example 1.

[0053] Comparative Example 5:

[0054] Comparative Example 5 differs from Example 1 in that all raw materials are added to a ball mill and milled for 4 hours using an alumina ball mill to obtain a foamed ceramic powder. The remaining conditions are the same as those of Example 1.

[0055] like Figure 1 As shown, the foamed ceramic material prepared in the embodiment of the present invention is composed of many pores of uniform size, and has good pore structure support and pore layout; on this basis, as Figure 2 As shown, a large amount of crystals are precipitated, thus giving the foamed ceramic material good mechanical properties.

[0056] The properties of foamed ceramics were tested according to the "Test Methods for Inorganic Rigid Thermal Insulation Products" (GB / T 5486-2008). The performance indicators of the foamed ceramic materials prepared in the examples of the present invention and the comparative examples are shown in Table 2.

[0057] Table 2 Performance indicators of foamed ceramic materials obtained in the embodiments of the present invention and comparative examples

[0058]

[0059] The foamed ceramic material of the present invention utilizes fly ash beads from power plants as a buffer, and realizes crystallization strengthening by controlling process conditions and combining secondary crystallization, so that the foamed ceramic products have higher compressive strength and lower thermal conductivity at a lower volume density, realizing the resource utilization of solid waste and having both light weight and higher mechanical properties.

Claims

1. A method for preparing a lightweight and high-strength foamed ceramic material using waste residue, characterized in that: The raw materials of the foamed ceramic material are composed of 51.3-69.3 wt% of metal slag, 14.8-21.4 wt% of feldspar, 1.0-1.7 wt% of foaming agent, and 14.9-25.6 wt% of buffer; the buffer is fly ash beads or fly ash with a fly ash bead content greater than 80 wt%; the metal slag is vanadium-titanium-iron slag and / or molybdenum slag; the feldspar is potassium feldspar and / or sodium feldspar; and the foaming agent is SiC dust collecting powder. The preparation method comprises the following steps: (1) dry-grinding the metal slag and feldspar to obtain a foamed ceramic base material; (2) adding a foaming agent and a buffer to the foamed ceramic base material and stirring and mixing them uniformly to obtain a foamed ceramic powder; (3) The foamed ceramic powder is filled into a mold, and the temperature is raised to 1140-1180°C at a rate of 3-8°C / min, and kept at this temperature for 60-100 min; then the temperature is lowered to the crystallization temperature of 950-1000°C at a rate of 2-8°C / min, and kept at this temperature for 3-5 h; and then the foamed ceramic material is obtained by cooling to room temperature at a rate of 2-6°C / min.

2. The method for preparing a lightweight and high-strength foamed ceramic material using waste residue according to claim 1, characterized in that: The particle size of the buffer is D50=45-55um.

3. The method for preparing a lightweight and high-strength foamed ceramic material using waste residue according to claim 1, characterized in that: The particle size of the foamed ceramic base material in step (1) is D50=45-55 μm.

4. The method for preparing a lightweight and high-strength foamed ceramic material using waste residue according to claim 1, characterized in that: The stirring time of step (2) is 30 to 60 minutes.

5. A product obtained by the method for preparing a lightweight and high-strength foamed ceramic material using waste residue as claimed in any one of claims 1 to 4.

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